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Genetic Engineering:
Transcription, Translation, and
Genetically Modified Organisms
8.1 Genetic Engineers
• Genetic engineers are scientists who
manipulate genes
• Manipulations include:
– Changing a gene
– Changing how a gene is regulated
– Moving a gene from one organism to
another
• In the early 1980s, genetic
engineers at Monsanto®
Company began producing
recombinant bovine
growth hormone (rBGH)
• The bacteria were given
DNA that carries instructions
for making BGH
• Growth hormones act on
organs to increase body size
and milk production
• Before genetic engineering,
the growth hormone was
taken from the brains of
slaughtered cows and then
injected into live cows
• This can also be
done to get human
growth hormone
from human
cadavers
– time consuming and
results in relatively
small amounts of
hormone
• When injected into
humans with
pituitary dwarfism,
they grow in size
From Genes to Protein
• How are proteins
made?
• Gene carries
instructions for building
a protein in a process
called protein
synthesis
• DNA  RNA 
protein
DNA
template
strand
TRANSCRIPTION
mRNA
TRANSLATION
Protein
Amino acid
Mutations
• Mutations to DNA
can affect proteins
Regulating Gene
Expression
• Different cells need
different proteins made
• The cells all contain the
entire DNA information,
but only use the genes
they need
• Cells regulate gene
expression, or the types
of proteins that are
made in that cell
• “turn on” or “turn off”
Cloning a Gene Using Bacteria
Step 1. Remove the Gene from the Cow
Chromosome
• The cow gene is sliced out using
restriction enzymes leaving “sticky
ends”
• Restriction enzymes cut DNA only at
specific sequences, called palindromes
“madam”
• The unpaired bases form bonds with
any complementary bases with which
they come into contact
Cloning a Gene Using Bacteria
Step 2. Insert the BGH
Gene into the
Bacterial Plasmid
• The bacterial plasmid is
also cut with the
restriction enzyme,
leaving sticky ends
– A plasmid is DNA that is
separate from the
bacterial genome
• This is now
recombinant
DNA
• The enzyme selected by the scientist cuts
at both ends of the BGH gene, but not
inside the gene
Cloning a Gene Using Bacteria
Step 3. Insert the
Recombinant
Plasmid into a
Bacterial Cell
• The recombinant
gene is then placed
into bacterial cells
• Large numbers of
these rBGH genes
are copied
• The bacteria produce the BGH protein
• This works, because bacteria use the same genetic
code as cows (and all living things)
• Other proteins are made in this way:
Bacteria Produce
Human
Proteins Like:
Insulin
Human Growth
Hormone
Anticoagulants
Interleukins
8.4 Genetic Engineers Can
Modify Foods
• Selective breeding
techniques have
affected foods for
thousands of years
• Genetic engineering
techniques (moving
genes from one
organism to another),
however, allow the
modification of food
much more quickly
Why Genetically Modify
Crop Plants?
• Increase shelf life,
yield, nutritive
value, pesticide
resistance,
herbicide
resistance,
drought
resistance, frost
resistance
• Some tomatoes
have been
modified to slow
ripening
Modifying Crop Plants
with the Ti Plasmid
• A Ti plasmid (tumor-inducing plasmid) can be used to insert a
particular gene into plant cells
Modifying Crop Plants
with the Gene Gun
• A device called a
gene gun inserts
pellets covered with
foreign DNA into the
cells of such crop
plants as corn,
barley, and rice
Genetic Engineers Can
Modify Food
• Transgenic organisms
are produced when a
gene from one
organism is
incorporated into the
genome of another
• The more popular term
for transgenic
organisms is GMO, for
genetically modified
organism
Genetically Modified Foods in
the U.S. Diet
• Half of all food in U.S. market contain at
least some GM foods
– Most soybeans grown are modified
for herbicide resistance
– GM corn – an ingredient in most
processed foods – is common as well
– GM canola and cottonseed oils are
used in a huge range of food products
How Are GM Foods Evaluated
for Safety?
• The EPA must approve all GM crops
• GM foods can cause allergic reactions
(8% of us are allergic to foods)
• Newly inserted genes may also encode
proteins that prove to be toxins
GM Crops and
the Environment
• Concerns over GM crops extend
beyond their impact on the human body:
– Effect on surrounding organisms
– The evolution of resistant pests
– Transfer of modified genes to wild
and weedy relatives
– Decreased genetic variation/diversity
GM Crop Effects on
Nontarget Organisms
• Plants are genetically
engineered to resist
pests
– decreases need for
pesticides
• Corn has been
genetically engineered
to resist corn borers
• Inserted gene from
bacteria for toxin that is
lethal to the corn borers
but not to humans
Gene Therapy
• Once the genetics are worked out, gene
therapy can be researched
• Replacing defective genes with
functional ones
– Germ line gene therapy in embryos
– Somatic cell gene therapy in
individual somatic cells in affected
tissues
Gene Therapy
• Treatment for SCID
(severe combined
immunodeficiency)
• Non disease causing
virus is genetically
engineered with the
functioning gene that is
needed in SCID
patients
• The virus infects the
immune cells and the
immune cells get the
functioning gene
Gene Therapy
• Genetically engineering
somatic cells requires
repeated treatments
• Somatic cells have
limited lifespans
• The condition may still
be passed to offspring,
because somatic cell
gene therapy does not
treat all the cells in the
body
• The only way to do this
is to have germ line
gene therapy
• Current somatic gene
therapy is not widely
used
• Only for single gene
disorders with cells that
can be removed,
engineered and then
replaced in the body
• Cloning is the making of entire
organisms using genetic
engineering
• Done in cattle, goats, mice, cats,
pigs, rabbits, and sheep
• Dolly the sheep was the first
animal to be cloned
• Dolly was put to sleep at the age
of 6 in 2003
• She was suffering from arthritis
and a progressive lung disease
• These are usually only seen in
old sheep
• There were 277 failures this
nuclear transfer technique
succeeded; Dolly was
successfully born in 1997
Cloning
Cloning
• Instead of cloning
entire organisms,
there is therapeutic
cloning
• Stem cells are
induced to turn into
specific tissue cells
or organs for
transplants